In recent years, there has been considerable concern regarding future energy needs due to eventual depletion of fossil fuels and to safety problems of nuclear power. Thus there has been renewed interest in research into various devices for converting energy in naturally occurring fluid streams or currents into electrical energy. For example, it has been estimated that there is enough power theoretically recoverable from ocean waves to satisfy present global demand for electricity.
Some prior art wave powered generators have turbine blades or the like designed to be rotated by wave motion. In efforts to reduce back resistance and energy loses on the return path of the blades; some known devices have been proposed with retractable blades. It has also been proposed to employ cup-like blades which have louvers which open to allow fluid flow through the blades during their return cycles of rotation.